Mass transfer columns, such as liquid vapor contact columns, are employed, for example, in distillation, absorption and stripping and typically provide for a liquid distributing means at the upper end of the column to distribute a liquid. The liquid is to be introduced at the upper section of the column more or less uniformly over the entire cross sectional area of the column before the liquid comes into an exchange relationship with an upwardly flowing gas. Generally the columns contain one or more, for example, a plurality of, gas-liquid contacting zones which comprise packing-type material, either a random or a structured-type packing material or a combination thereof, positioned in the column to effect the efficient contact between the upwardly flowing gas and the downwardly flowing liquid.
Generally, liquid distributors comprise a trough-like arrangement or pipes generally arranged in a parallel relationship across the cross section of the column and containing therein overflow channels at a defined level for the liquid to overflow the pipe or trough and to be distributed generally uniformly over the cross section of the column. In particular, a liquid distributor means may employ a central parting box as a predistributor means which generally extends perpendicularly to the parallel arranged troughs and into which parting box a liquid is fed from a pipe and from which predistributing means liquid is fed to the distributors for uniform distribution throughout the column. It is known that good liquid distribution is essential to obtain the proper performance for gas-liquid contact in a packed column. The proper liquid drip point distribution and maintaining such drip point distribution has been the subject of numerous publications and patents. It is particularly important to obtain good liquid distribution to prevent fouling at low liquid distribution rates, which is difficult since the holes used for liquid distribution are small in diameter and may tend to plug in use. It is therefore desirable to provide for an improved, efficient liquid distribution in a gas-liquid contact column so as to provide better distribution to the underlying packing in the gas-liquid column and to provide an open structure which facilitates cleaning of the multiple point drip structure and the flow orifices.
U.S. Pat. No. 3,491,792 discloses a vapor liquid distributing column which employs a plurality of generally parallel troughs and a central meter box to distribute a liquid to the packing below, the troughs having an upper portion of a gradient width and a lower portion of substantially constant width. German patent DE No. 27 52 391 C2 concerns a trough-type liquid distributor with a plate spaced apart from the side of the liquid distributor, the plate having multiple drip points at the lower end thereof and a material between the plate and the outside of the trough to provide improved distribution of the liquid. German patent DE No. 29 45 103 C2 relates to a trough-type liquid distributor with slotted openings in the side and containing a plurality of outwardly extending fingers to serve as drip points for the distribution of the liquid into the lower packing. German patent DE No. 30 13 782 A1 describes a trough-type liquid distributor with extending and bent fingers at the lower level thereof to provide for efficient distribution of the liquid issuing from the side orifices of the trough.
Other patents include U.S. Pat. No. 4,264,538 which describes an overflow liquid distributor for a packed column and which discloses a lower serrated portion extending downwardly from the trough and composing a number of angularly disposed drip portions and edges to direct the liquid flow over a uniform cross section area of the contact tower. U.S. Pat. No. 4,479,909 is directed to a distributor which includes a plurality of tubes having openings spaced apart on the upper sides of the distributor leading to respective troughs. The liquid is spread from the troughs by capillary channels which carry the liquid through slits in the wall of the trough onto various protruding tongues spread out below the tube to effect efficient distribution of the liquid from the troughs across the cross section area of the column. U.S. Pat. No. 4,476,069 relates to a liquid distributing apparatus which employs orifices in the side of a liquid distributing trough with the orifice being sized such that they stay submerged which includes adjacent vertical drip rods for the downwardly flowing liquid to provide good distribution of the liquid at low flow rates across the cross sectional area of the column. U.S. Pat. No. 4,648,972 concerns a liquid distributor wherein the high walls of the parting box or predistribution means are covered with a wettable, open pore material so as to provide improved and even distribution of liquid feed in the vapor-liquid contact tower.
Thus, the prior art has provided a number of this type of liquid distributors for gas-liquid contact towers and includes distributors having tongues or extensions or drip points below the trough or liquid distributing means. It is desirable however to provide for an improved liquid distributor for gas-liquid contact towers wherein there is improved efficiency in distribution of the liquid across the cross sectional area of the column and which distributor avoids some of the disadvantages and difficulties associated with manufacture and use of prior liquid distributors in gas-liquid contact columns.